1. Field of the Invention
The present invention relates to a sheet processing unit and an image forming apparatus with the same, and more specifically, a sheet processing unit which aligns and staples sheets that are ejected from an image forming apparatus such as a copying machine or a printer after image forming and an image forming apparatus with the same.
2. Description of the Related Art
Conventionally, a sheet processing unit has been proposed in which sheets ejected from the main body of an image forming apparatus such as a copying machine or a printer, etc., are conveyed one by one onto an ejecting mechanism processing tray and aligned or aligned and stapled (bound), and then ejected onto a stacking tray.
Furthermore, another sheet processing unit has also been proposed in which the first two or three sheets of one sheet bundle to be processed are overlapped together and delivered to bundle ejecting rollers of an ejecting mechanism, and the sheets are butted against a stopper of the processing tray by rotating the bundle ejecting rollers rearward, whereby the plurality of sheets are aligned or aligned and stapled.
However, in an image forming apparatus main body in which sheets are conveyed at small intervals at a high speed to the sheet processing unit, in some cases, the sheet aligning operation or the operation of ejecting sheets onto a tray cannot be completed within the sheet conveying interval.
Furthermore, conveying of sheets at small intervals at a high speed or repetition of the sheet aligning operation for each sheet easily deteriorates the aligning mechanism due to an increase in size of motors in accordance with the high-speed aligning operation or the large number of times of the aligning operation.
Therefore, a sheet processing unit has been proposed which is provided with a sheet stacking mechanism which stacks a predetermined number of sheets successively conveyed from an image forming apparatus main body so that sheets are retained until a predetermined number of sheets are stacked and then conveyed to the ejecting mechanism (Japanese Patent Laid-Open No. 1998-181981).